DESCRIPTION: (Applicant's Abstract) There is an increasingly large population receiving opiates on a chronic basis, either for treatment of opiate dependence or for treatment of chronic pain. Managing pain in opiate maintained individuals is a challenging problem. The development of opioid tolerance and dependence may result in altered pain sensitivity and subsequent response to additional opioids. Many clinicians believe addicts cannot benefit from further opiate administration because they are tolerant to the analgesic effects. Others believe that if an addict is maintained on an opiate agonist, that medication provides adequate analgesia for acute pain. Patients are reluctant to give accurate histories because clinicians often withhold opioid analgesics from patients with a history of drug abuse. Those who do complain are viewed suspiciously and their complaints ignored. Currently there are few guidelines to assist clinicians and those that do exist are based on experience and consensus rather than evidence-based research. This study proposes to examine: 1) how patients on opiate maintenance (either buprenorphine or methadone) experience pain (tolerance and threshold) and how they are different from non-opiate dependent individuals, 2) how patients maintained on methadone and buprenorphine differ from normal controls in response to added opiate and non-opiate analgesics and 3) how therapeutic plasma concentration levels of morphine for analgesia differ in methadone and buprenorphine maintained patients compared to normal controls. The results of this proposed study will help develop systematic guidelines for clinicians in the management of pain in opiate maintained individuals.